Broaching tool



pril 29, 1924., 1,492,252

` E. J. LAPOINTE 'BROACHING TOOL PTNF @FFHQO rois a'. nnronvrn, or ANN non, MICHIGAN.

BROACHING TOQL.

@riginal application filed December 2, 1921, Serial No. 519,500. Divided and this application tiled April To all whom it may concern.'

Be it known that 1, FRANCIS J. LAPOINTE, a citizen of the United States of America, and a resident of Ann Arbor, in the county of Washtenaw and State of Michigan, have invented certain new and useful Improvements in Broaching Tools, of which the following is a specification.

This invention relates to broaching tools and particularly to tools of this character designed to cut and finish round holes.

The present invention consists in forming the tops of the teeth of an equal thickness with the backs thereof connected to the bevel portions of the broach by a slight shoulder, the face of which is parallel with the front face of the teeth.

The invention further consists in certain novel features of construction and arrangement of parts which will be underst-ood readily by reference to the description of the drawings and to the claims to be hereinafter given.

For the purpose of illustrating the invention, one preferred form thereof is shown in the drawings, this form having been found to give satisfactory and reliable results, although it is to be understood that the various instrumentalities of which the invention consists can be variously arranged and organized, and that the invention is not limited to the precise arrangement and organization of the instrumentalities as herein shown and described, except as required by the scope of the appended claims.

Of the drawings:

Fig. 1 represents an elevation of a broach embodying the principles of the present invention.

Fig. 2 represents a section of same on line 2, 2 on Fig. 1, and

Fig. 3 represents a greatly enlarged sectional detail showing the differences in formation of the successive teeth.

Similar characters indicate like parts throughout the several figures of the draw- Y n the drawings, 10 is a member having a cylindrical portion 11 at one end and another cylindrical portion 12 at the opposite end.

The portion 12 is of larger diameter than the portion 11 and is adapted to burnish the hole when the broaching has been completed.

Adjacent `to the cylindrical portion 12, the

Serial No. 632,318.

member 10 is provided with a plurality of annular cutting members 13 having the same diameter as the portion 12.

These cutting members 13 are preferably spaced an equal distance apart.

Between these cutting members 13 and the portion 11 are a plurality of cutting members 14 which are spaced from each other a distance considerably greater than the distance between the cutting members 13.

Preferably the space between every alternate pair of cutting members 14 is greater than the space between the other pairs as clearly indicated in the drawings.

Usually in broaches of this character, the cutting members 13 and 14 are backed off slightly from the cutting edge, and the member 10 is then provided with a groove 15 to receive the chips cut by the tool.

One wall of this groove 15 forms the front face 16 of the cutting members 13, 14 while the other wall 17 is inclined tothe rear edge of the cutting tooth.

Each cutting member 14 has a diameter slightly greater than the cutting member in advance thereof.

lVhen the broaches are straightened in the manufacture thereof, it is extremely difficult to straighten them so that they will run true within .O05 -to .010 of an inch and it is often necessary to grind them running this much out of true.

The consequence is that it is difficult to secure a perfectly round periphery as some parts of the periphery will be wider than other parts and this prevents the grinding wheel from cutting as freely when on a wider portion as it does on a narrow portion of said periphery.

This is particularly true in the manufacture of small broaches.

This is also true when the teeth are backed ofi' in an attempt to secure a uniform land for a cutting edge.

Unless the land is of uniform width, an imperfect result will be obtained during the broaching operation due to the fac-t that if one side of the land is wider than another side, it will cut freer on that side and will. crowd the broach over to one side with t-he result that a hole is produced that is not in proper relation to the original hole in the work being operated upon.

By providing the shoulder or rear face 18, these difficulties are entirely obviated a'perfectly and a perfectly round tooth may be ground and when the broach is in use, owing to the uniform width of the periphery ofA the tooth,

relation to the original hole in the work. Moreover, the construction of the broach is greatly simplified by making the teeth with the shoulder or face 18. v

The teeth 14 are preferably provided with a plurality of peripheral nicks or indentations 19, the nicks ineach tooth being out of alinement with the nicks in the teeth adacent thereto. Y

n applicants broaching tool, it is quite essential'that the two faces 16, 18 be parallel, for in the construction o the broach, the device must be tempered before the cutting members 14 are ground; and in tempering, the broach is liable to become dis- 2o`torted and while 'distorted the cutting members must be ground so that these members will be in axial alinement when the vided with a plurality of cutting members,

' ding is completed.

If the larger end of the cone-shaped portions 17 registered with the "periphery of the cutting members 14, it is obvious that with the entire tool distorted to some extent,

when the grinding of the cuttingv member 14 is effected, the width or thickness of the eriphery of the cutting member would be iable to vary at different points about the periphery.

In such a case, the tool would operate imperfectly and would not cut a clean,

round hole, but would, on the contrary, be liable to move sidewise to some extent and the hole cut would, as a consequence, be out of round.

'This would be very objectionable and to obviate this difficulty, applicant has provided the cone-shaped connecting portion 17, the diameter of the end abutting the rear face of the cutting member 14 being slightly less than the diameter of said rear face 18.

The cone-shaped portions 17 stifien the tool and reduce to a minimum the distortion during the tempering.`

vBy causing the larger end of the conical portion 17 to 'oin the cutting member 14 at a point slig tly inside the periphery ot' the cutting member 14, a rear face 18 is formed absolutely parallel to the front face 16 which extends inwardly from the periphery of the cutting member approximately six times as "far vas the rear face 18 extends inwardly from. said periphery.

round hole will be cut in proper 12th day'of When thus constructed, even if the tool is somewhat distorted during tempering, the thickness of the cutting member 14 will be the same throughout, after the grinding operation has been completed.

By providing this rear face 18, this desired result can always be obtained, even if theportions 17 are slightly out of alinement, and a tool formed in which the cutting members will be in alinement and capable of cutting a round hole without any tendency for the tool during the cutting operation to veer sidewise.

The present invention is a division of the application filed December 2, 1921, Ser. No. 519,500.

It is believed that the operation and many advantages of the invention will be understood readily without further description.

1Having thus described my invention, l c aim:

1. A device of the class described, pro- 2. A device of the class described, pro-l vided with a plurality of cutting members, the front and rear faces of which are parallel and perpendicular to the axis of said cutting member, each pair of cutting members being connected by portions, the diameter of the end connected to the rear face of a cutting member being slightly less than that of sai-d rear face and greater than the diameter of the end connected to the front face of the next cutting member.

3. A device of the class described, provided with a plurality of cutting members, the front and rear faces of which are parallel and perpendicular tothe axis of said cutting members, the front face of each cuttin member'extending inwardly from the periphery of said cutting member approximately six times as far as the rear face extends inwardly from said peripher Signed by me at Ann Arbor, ich., this April, 1923.

. FRANCIS J. LAPOINTE.

Witnesses:

Roscon O. BoNisTnEL, D. A. DE LONG. 

